Electronic visual inspection device having spaced phototubes



March 7, 1950 J. c. FROMMER 2,499,910

ELECTRONIC VISUAL INSPECTION DEVICE HAVING SPACED PHOTOTUBES Filed Nov. 3, 1948 2 Sheets-Sheet l 11/ IIIIIIIIIIIIIIIIIIII 11/1/11 III 1/ I 1/ 1111 1/11/11! III IIIIII 11ml! 1 1/ 1 1 1 fIIIIIIIIII IIIIIIIIII IIIIIIIIIIIIIIIII IAIIIIII IIIIIIIIIIIIIfIl/I 1! I 11111 FIG. 7

F10. F10. 5 F 1 6 INVVENTOR.

c/OfiZ'PH 6'. FROMJER BYW A T TORJVEY March 7, 1950 J c FROMMER 2,499,910

ELECTRONIC -vIs'uAL INSPECTION DEVICE HAVING SPACED PHOTOTUBES Filed Nov. 5, 1948 2 Sheets-Sheet 2 Fla. 3 r

Focus AHA MM INTENSITY 37 A T TORNE'Y Patented Mar. 7, 1950 UNITED. STATES ELECTRONIC VISUAL INSPECTION DEVICE HAVING SPACE!) PHOTOEUBES (Cl. SSa-JA).

5 Claims.

This invention relates to an electronic device and circuit for rapidly and visually inspecting an object for a dimensionalcharacteristic.

'Inmany operations, accurate checking or de termination of a dimensional characteristic of an object 'is essential but control of an'operation giving that dimensional characteristic, is not essential. Electronic'inspection devices for rapidly sorting objects according to a dimensional characteristic or for quickly controlling a previous operation, if a dimensional characteristic of an object does not meet a predetermined standard, are well known. Also are known slow acting devices having electric bulb indication means for making dimensional inspections visually. But, heretofore, there has been no de' vice for obtaining a constant visual check of a series of dimensional characteristics of an object or objects wherein it is desired to check such characteristics at an extremely rapid rate, say 100 to 1000 per minute. It is obvious that flashing light bulbs cannot do this. In such operations to which my invention applies, it is not essential that an immediate and constant adjustment by elaborate control equipment be used, although my invention is useful therewith. It is essential in such operations that rapid visual indicating means be provided .in order that an operator can make manual adjustments of the machine operating on the object.

Specifically, a typical operation for which my invention is useful involves a punch press operating on a waxed paper wrapping ,for bread. The press punches holes in the wrapper at regular and closely-spaced intervals. The punched wrapper comes oil the press at a speed of about 100 feet per minutes and there are around 4 holes per foot. It is desired to inspect the spacing of the holes in the wrapper as it leaves the press in order to make manual adjustments of the press if the spacings are not regular and uni form. Thus in this particular case visual inspection at the rate of 400 per minute is required.

It is an object of my invention to provide a device for making inspections of the type referred to above.

I accomplish this object by passing the object or objects to be inspected through an optical scanner having light sources and phototubes so positioned as to receive light through the punched holes, together with the provision of an oscilloscope controlled through a novel electronic circuit due to the light received by the phototubes, so that visual inspection can be made by watching the screen of the oscilloscope.

Gther advantages, objects and uses of my invention will become apparent byreferringtothe drawings, in which:

Figure 1 is perspective view ofa portionof the optical system showing the position of thelight sources in relationship to'the holes in the punched wrapper heretofore referred to.

Figure 2 is across-sectional elevation of the optical system.

Figure 3 .illustrates -the cathode ray tube and the electronic amplification circuit used in my device.

Figures 4-6 inclusive illustrate differentscreen or scope patterns obtained with my inspection device.

Figure 'T-illustrates the-use of a scale for indicating-theextent of'the variation from the standard of the dimensional characteristic being'inspected.-

Figure 8 illustra'tes the arrangement of the op ticalsystem for inspecting a series of articles for length.

Figures 1 to '7inclusive are described in connection with-'inspecting the spacing of holes in a wrapper resulting from a punch press operathrough the inspection zone, such as the article illustrated in Figure 8.

Referring to-Figures l and 2, the general scanner arrangement and optical system is indicated by numeral 4. The punched wrapper 5, is passed through the inspection zone I in the direction of the arrow 6. The inspection zone I is the space between the lamp sources 8, 9, and it, and the phototube shields l 5, l2, and I3.- It is the distance 14, that is to be measured on the wrapper or web '5, which distance indicates the spacing of the punched holes 15'. Lenses it are provided for properly focusing the light beam from the light sources. Phototubes I, 2 and 3 are positioned within screens I3, ['2' and M respectively, having light admission openings l1, l8 and 59 respectively.

As the punched material passes through thedistance between phototubes 2 and 3 is adjustable so that they may be located at the exact distance apart which equals the correct hole spacing in the screens or masks. The holes 18 and IS in the masks l2 and [3 are rectangular and are aligned and centered with the holes [5 in the punched material 5. Thus, as the edge of a hole passes over the phototube mask at a constant rate, light strikes the phototube and the amount of light increases until the punched hole has uncovered the entire opening in the phototube mask.

Reference will now be made to the amplifying circuit shown in Figure 3. Phototube l is used to initiate the circuit and to regulate the intensity of the spot (the electrical discharge) in cathode ray tube 20. Phototube I when it receives light slightly ahead of the other phototubes, initiates an electrical pulse which is first amplified by the amplifying tube 2|. The amplified pulse, which must be positive for the circuit shown, is fed through condenser 22 to the grid 23 of the cathode ray tube 29 which results in momentarily increasing the intensity of the electron beam in the cathode ray tube to the point where it will make a visible spot on the tube screen 24, as illustrated in Figures 4 to 7 inclusive. Components are selected so that the spot will remain bright during the measuring process only.

As is known, the position of the spot on the cathode ray tube screen 24, is determined by the electrostatic deflection plates 25, 26, 21, and 28, the beam being deflected toward the more positive plate. The plates are provided in pairs as shown so as to control the beam in two planes at right angles to each other. Adjustment of the intensity is made by the point of contact with the adjustable resister 31.

The focusing of the cathode ray tube is obtained by connecting the screen grid of the tube to the adjustable resister 36 at a point less negative than the cathode.

The cathode ray tube and its component parts are referred to herein and in this art as an oscilloscope.

In operation, the potentials applied to plates 25 and 21 are so adjusted by resisters 29 and 3!] that the normal position of the spot is along a diagonal of the square formed by the projection of the plates on the screen of the tube. Now when the potential is increased on deflection plate 28, the spot will move from its original position in direction of that plate. The amount of movement is directly proportional to the increase in voltage so that if a steadily increasing voltage is applied, the spot will move steadily toward deflection plate 26. Likewise, if voltage is applied to deflection plate 28, the spot will move toward it. Applying voltage to both deflection plates 26 and 28 simultaneously and at the same rate of increase, causes the spot to move along the diagonal referred to above.

As phototubes 2 and 3 begin to receive light, they cause the grids of their respective amplifying tubes 3! and 32 to become more negative. This decreases the voltage drop across resistors 33 and 34 respectively by decreasing the flow of current through the amplifying tubes 3| and 32. Deflection plates 26 and 28 are also connected respectively to adjustable resistors 33 and 34. Thus as the voltage drop decreases across resistors 33 and 34, the deflection plates 26 and 28 cause movement of the spot on the cathode ray tube screen 24 as described above. Such movement continues until the holes in the phototube masks are completely uncovered by the holes in the punched material. The amount of movement is controlled by the point at which the deflection plates 26 and 28 are tapped into the resistors 33 and 34. In operation, these are adjusted to be exactly equal and of such an amplitude that the movement of the spot will fall within the calibrated pattern positioned over the cathode ray tube screen 24 as shown in Figure 7.

In the case where the two punched holes in the wrapper are correctly spaced and exactly equal to the distance between the holes in the masks for phototubes 2 and 3, equally increasing voltages will be applied simultaneously to deflection plates 26 and 28. This will result in a screen pattern as shown in Figure 6.

When the punched holes in the web 5 are too far apart, phototube 2 will start receiving light before phototube 3. This results in voltage being applied to deflection plate 26 before plate 28 and during the intervening time, the spot will move directly toward deflection plate 25. When phototube 3 begins receiving light, deflection plate 28 will then come into action and the course of the spot will change as shown in Figure 4. Similarly when the holes in web 5 are too close together, the voltage on plate 28 is given a head start" over that applied to plate 26 and a screen pattern as indicated by Figure 5 is obtained.

The variation and direction in screen pattern when the distance between the holes departs from a standard dimension, can be determined by using the calibrated screen of Figure 7. The punch press operator need watch only the screen of Figure '7 and make his adjustments accordingly.

Thus I have provided visual means for rapidly checking a dimensional characteristic of an article. This principle of my invention obviously has many applications, one of which is illustrated in Figure 8 in which it is desired to check the length of a series of articles 35. In such an application phototubes 2 and 3 would be spaced at a distance equal to the length of the standard article and phototube i would be placed between them. As the objects 35 were passed through the inspection zone, the front edge of the object would interrupt the light beam to phototube l and start the measuring cycle as described previously. Then the circuit of Figure 3 would actuate the cathode ray tube screen such as to indicate whether or not the front edge of article 35 started interrupting the light to phototube 2 before light began to fall on phototube 3.

Since in the operation shown in Figure 1, both phototubes 2 and 3, for the circuit illustrated in, and described for Figure 3, operate on. an increase of light during the checking period, it would be necessary to slightly modify the circuit of Figure 3 in order to obtain the type of inspection desired for Figure 8. This could be done in one of several conventional ways and therefore additional drawings and descriptions are not deemed necessary. For example, such modification could be accomplished by reversing the polarity of the voltage applied to phototube 2, reverse the connections to deflection plates 25 and 28, or add an inverter amplifying the stage between amplifier 3i and the plate 28. Otherwise the electrical circuit of Figure 3 would be the same.

To get exact indication of slight deviations it is necessary to have the illumination of the photocell to be exactly proportional to the uncovered area. For this purpose I provide uniform jective lenses 36 and 31 as shown in Figure 1.

In Figure 8 since the holes in masks are in immediate contact with the article 35, such objective lenses are not needed.

Other applications of my invention to other types of inspection operations as well as other modifications to the electronic circuit are possible within the scope 01 the following claims.

I claim as my invention:

1. A visual inspection device for making a series of inspections of a dimensional characteristic of rapidly moving articles, comprising an optical system including light source means and two phototubes, and an inspection zone through which said articles pass, said light source means being positioned to direct light through the inspection zone to the phototubes, said phototubes spaced in said inspection zone consecutively along the path of movement of said articles at a spacing corresponding to the standard dimensional characteristic of the article thereby defining the limits of said dimensional characteristic, said phototubes thereby being placed in different conditions of illumination by said light source for standard and non-standard articles passing therethrough, an oscilloscope comprising a cathode ray tube and a visual screen, said oscilloscope having opposing pairs of deflecting plates, each of said phototubes separately connected through amplifying means to said opposing pairs of deflecting plates whereby their voltage is controlled and the electronic spot passing between said plates and appearing on said screen is controlled in accordance with the condition of illumination of said phototubes, and said screen serving as visual means indicating Whether or not said series of dimensional characteristics conform to the standard.

2. The apparatus of claim 1 further defined in means for fixing the intensity of the beam passing between said plates comprising means varyin the grid potential of said cathode ray tube operatively connected to a third phototube positioned in said inspection zone relative to the movement of said articles to receive light in accordance with a predetermined position of said article passing through said inspection zone independently of the light received by the two phototubes indicating the dimensional characteristic of the article.

3. A device for indicating the distance between two lines separating regions of difierent optical properties on an object moving continuously transverse to said lines comprising an optical device having an inspection zone, means for moving said article continuously through said inspection zone, a pair of phototubes with means for illuminating each of said phototubes, said illuminating means being positioned to direct light through the inspection zone to the phototubes, said phototubes positioned consecutively along the path of movement of said object such that one of the lines separating regions of different optical properties passes adjacent to one of said phototubes simultaneously with the passage of the other of said lines adjacent to the next consecutive phototube thereby affecting the illumination of said phototubes and the resulting current developed therein, an electronic circuit comprising a cathode ra tube having a screen and two pairs of deflecting plates which function to vary the position of a luminous spot on said screen with variation in the potential applied to said plates, means connected with one of the phototubes responsive to the current developed therein for controlling the deflection potential across one pair of said plates and means connected with the other phototube and responsive to the current developed in the other phototube for controlling the deflection potential across the other pair of plates, whereby the shape of the image traced by said luminous spot varies with and indicates the distance between said lines.

4. A device as defined in claim 3 for the inspection of the distance between two edges of opaque objects including two masks having openings therein for admitting light positioned between the object and each of the two phototubes respectively and in the immediate vicinity of the path of said opaque objects such that when one of said edges reaches the opening in one of said masks the other of said edges simultaneously reaches the opening in the other of said masks.

5. A device as defined in claim 3 for the inspection of the distance between two edges of opaque objects including two masks positioned in front of the two phototubes respectively and optical means to produce an image of one of the two edges on one of said masks and of the other of said edges on the other of said masks at the moment of the simultaneous passage of said edges adjacent to said two phototubes.

JOSEPH CHARLES FROMMER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,067,262 De Montignier Jan. 12, 1937 2,085,671 Powers June 29, 1937 2,290,606 Burnett July 21, 1942 2,324,270 Schlesman July 12, 1943 2,333,758 Xemis et al. Nov. 9, 1943 2,402,405 Hurley June 18, 1946 2,455,532 Sunsten Dec. 7, 1948 

